The present invention relates generally to tools used in tensioning bundle ties and more specifically to a bundle tie tensioning clutch to be used in a bundle tie tensioning tool.
Flexible bundle ties are well known items. Such ties are used to secure wires, cables, tubing and similar items into tight, neat bundles. Typically, flexible bundle ties include a head portion and a tie tail portion extending from the head. In use, the tie tail is looped around the items to be secured and then inserted through the head. A locking or ratcheting mechanism in the head holds the tie tail in the head and secures the tie around the bundle. Preferably, the tie tail is pulled through the head under tension to draw the items to be secured into a tight bundle. Thereafter, the excess portion of the tie tail may be clipped off near the head.
Many flexible ties are economically molded of flexible plastic. For some applications, however, plastic has insufficient strength or other drawbacks, and metal ties are used. Metal ties include a flat strap portion and a locking head portion, each of which is made of a strong, durable metal such as stainless steel. As a rule, metal ties are significantly stronger than plastic ties of the same size and are typically pulled at much higher tensions than plastic ties when they are installed.
A variety of tools have been developed to enable workers to install flexible bundle ties with speed, uniformity and economy. Generally, such tools function to grip the tie tail portion of the tie after the tie has been looped around the items to be bundled. The tool pulls the tie tail until a predetermined desired tension is achieved, after which the tool cuts off the excess portion of the tie tail closely adjacent the head. Such tools greatly simplify the task of properly installing bundle ties.
In a typical tie tensioning tool, a tie is grasped and pulled by a tensioning clutch including a pawl, a pawl link, a shaft, a torsion spring, and tension abutment such as a backing plate. The tensioning clutch is generally slidably situated in a housing. The pawl link usually includes a yoke in which the pawl is rotatably supported on the shaft. The torsion spring includes a substantially stationary leg that cooperates with an aperture in the pawl link, and a biasing leg that cooperates with the pawl, thereby biasing the pawl toward the backing plate.
Various handheld tools have been developed to assist in the installation of flexible ties. In one well known form of such tool, the tool comprises a pistol or gun-like device having a movable trigger or lever that is squeezed by the operator to pull on the tie tail and thereby tension the tie. The operator continues squeezing the trigger until a predetermined tension is achieved after which a cutting blade adjacent the nose of the tool snaps upwardly to clip off the excess portion of the tie tail. A knob at the rear of the tool allows the worker to adjust or set the tension at which cutoff occurs. Examples of such manually operated handheld tools are shown in the inventors' U.S. Pat. No. 4,997,011, issued Mar. 5, 1991, U.S. Pat. No. 4,793,385 issued Dec. 27, 1998, and U.S. Pat. No. 5,921,290 issued Jul. 13, 1999, commonly owned by the assignee hereof.
The pawls of prior devices were normally cast in hardened steel and had teeth, which gripped a tie when the tie was inserted between the pawl and the cooperating tension abutment or backing plate. The pawl is a wear part of a tensioning tool. That is, eventually and frequently, the teeth on the pawl wear down and the clutch needs to be repaired or the pawl replaced. This is especially true when the tensioning tool is used with metal ties, such as stainless steel ties. Replacing or repairing a damaged or worn pawl is both time and labor intensive. Most prior devices require that the tool be taken out of service for repair, and replacement of the pawl requires disassembly of the tool's housing. As with any industrial teardown repair, care must be taken to ensure that reassembly is properly executed, and the tool must be tested prior to reinstatement of service.
Therefore, the art of tensioning bundle ties may benefit from a bundle tie tensioning clutch having an engagement surface that may be changed when desired, without significant disassembly of the remainder of the tensioning tool.